System Freezes when using 2 GPU

[Valansch]

Hello fellows!
I hope to move this to the support forum when i'm "trusted"^^
Sry if this is a double post, but my first one kinda didn't make it :O
I have a severe Problem with mining.
I use CGminer and whenever i use both of my R9 280X in any way at the same it will mine for 1-5 seconds unti my system freezse completly. I know the GPUs aren't working while this happens because i only use 150W while it is frozen.
I'm using a brand new 64-bit win7 ultimate with ATI Catalyst Suite 13.12 and cgminer-3.7.2-windows.

I'm starting just by double clicking on the miner, since i have it all configured in the cgminer.conf. I get the same error, when i use a *.bat with the configs in it.

My cgminer.conf

Code:

{
"pools" : [
	{
		"url" : "http://coinotron.com:3334",
		"user" : "Valansch.3",
		"pass" : "3"
	},
	{
		"url" : "http://coinotron.com:3334",
		"user" : "Valansch.4",
		"pass" : "4"
	}
]
,
"scrypt" : true,
"intensity" : "13",
"vectors" : "1",
"worksize" : "256",
"thread-concurrency" : "8192",
"shaders" : "2048",
"api-port" : "4028",
"gpu-threads" : "2"
}

When i add a "device" : "0" or "device" : "1" everything works fine with just the one GPU in use, i also tried running 2 instances of cgminer--> no sucess

My System + Hardware:

Code:

Windows 7 Ultimate 64 Bit
CPU: AMD Athlon II X2 250 Processor
Mobo: AsRock 990FX Extreme3 AMD 990FX Dual Channel
PSU: 850 Watt MS-Tech Value-Edition retail Non-Modular
Ram: 1x 2048 MB Kinston Value Ram DDR3-1600
GPU 0: Powercolor Radeon R9 280X (in Slot 0)
GPU 1: Sapphire Radeon R9 280X (in Slot 4)

I would really appreciate any help!


PS: I'm sorry if there are any grammar or spelling mistakes. It's not my first language have mercy   But if you finde a mistake feel free to shoot it!

[pontiacg5]

This sounds like a incorrectly loaded multi-rail PSU.

I found this online, it is in another language but the good stuff is there.

Modellserie:    Value-Edition retail
Leistung:    850 Watt
Kühlung:    140mm Luefter
Spezifikation:    ATX 2.3
Effizienz (bei 230V):    80%
80 Plus Zertifikat:    80+
+3,3V:    22 Ampere
+5V:    24 Ampere
+5Vsb:    2.5 Ampere
+12V1:    27 Ampere
+12V2:    27 Ampere
+12V3:    nicht vorhanden
+12V4:    nicht vorhanden
+12V5:    nicht vorhanden
+12V6:    nicht vorhanden
+12V7:    nicht vorhanden
+12V8:    nicht vorhanden
-12V:    0.3 Ampere
Anschlüsse:    1x ATX 20/24pol, 1x ATX12V 4+4pol, 1x PCI Express 6pol, 1x PCI Express 6+2pol, 1x 3.5 Zoll, 4x 5.25 Zoll, 8x SATA
Kabelmanagement:    Non-Modular
Besonderheiten:    active PFC

You see +12V1 and +12V2? This means your power supply is a twin 12V rail supply. This tells us that each rail is capable of 27A, or 27x12= 324W

If for some reason you have both graphics cards running on only one 12V rail it will cause that one rail to overload and crash.

The solution is trying to find a rail output chart, so you can be sure both GPUs are on different rails, but that chart is not always made available. The next best thing to try is moving power connectors around to see if you can find the rails yourself.

It is also possible that your power supply is cheap and over-rated, lets just say 10%. That cuts 324W down to 291W. A 280X has a TDP of 250W, and can take much more if overclocked/not undervolted. If this is the case it may not be possible to run both a GPU and CPU/mobo on one 12V rail. You will need a new power supply in this case.

Good luck! Power supply issues are fun.

[Valansch]

Thanks for the quick answer!
Actually it's german and i'm german so it's fine!
I didn't know this was a problem, i bought 2 PSU because i wanted to have 4 cards, that is gonna be easy to test out.
Give me a couple minutes!